(1) Field of the Invention
The present invention relates to a human detection device which detects a walking human through an image processing, and in particular, a human detection device which detects the position of presence and gait direction of a human.
(2) Description of the Related Art
Much of the conventional human detection art utilizes a still image or a single differential image. In the case where human detection is executed using a still picture or a single differential image, because it is difficult to predict a shape characteristic change of a human which can arise from screening, etc. at the time of design, there are cases of false detection, non-detection, and so on. However, with a method which utilizes an image sequence, because interpolation and a prediction mechanism can be utilized in response to a temporary fluctuation in the quantity of characteristics that arises from screening, etc, a robust detection can be expected even with screening and a temporary environment fluctuation.
Conventionally, as a human detection art which utilizes a moving picture sequence (the first conventional art), a method is provided in which a human is detected through generating a three-dimensional spatiotemporal image by arranging images in temporal direction, extracting a spatiotemporal fragment image which cuts the three-dimensional spatiotemporal image along the ankle location of the human per frame, and executing detection of a periodicity unique to the human gait (for example, Niyogi, Adelson, “Analyzing and Recognizing Walking Figures in XYT,” MIT-TR-223, 1994, Page 3 and FIG. 3). Through this, it is possible to distinguish between a human and another moving body, and furthermore, by utilizing an image sequence, stable human detection is possible even with temporary change in environment.
In addition, as a different conventional art (the second conventional art), a method is provided which places a plurality of slits in an image, forms a moving body image utilizing a temporal pixel value change of the slit area, and assesses the movement direction of a moving body as well as counting (for example, Japanese Patent Application No. 3183320, Page 7 and FIG. 4). With this art, stable detection of a human and determination of the movement direction becomes possible by considering the temporal change of a human passing the slits.
However, in the aforementioned first conventional art, the art is limited to the case where the ankle position of the human is already known, and walking occurs only in left-right directions throughout the image. Additionally, as it is necessary to detect the ankle position in advance, initial detection of a human is a prerequisite. Therefore, there is a problem in that it is difficult to detect a human walking in various directions within the image.
In addition, in the aforementioned second conventional art, while it is possible to detect the gait direction through placing a plurality of slits for detecting a human throughout an image, it is necessary for a designer to decide the slit position in advance. Therefore, there is a problem in that the area in which human detection can be executed throughout the image is limited.